Liquid-jet photoemission spectroscopy (LJ-PES) directly probes the electronic structure of solutesand solvents. It also emerges as a novel tool to explore chemical structure in aqueous solutions, yetthe scope of the approach has to be examined. Here, we present a pH-dependent liquid-jet photoelectronspectroscopic investigation of ascorbic acid (vitamin C). We combine core-level photoelectronspectroscopy and ab initio calculations, allowing us to site-specifically explore the acid-base chemistryof the biomolecule. For the first time, we demonstrate the capability of the method to simultaneouslyassign two deprotonation sites within the molecule. We show that a large change in chemical shiftappears even for atoms distant several bonds from the chemically modified group. Furthermore, wepresent a highly efficient and accurate computational protocol based on a single structure using themaximum overlap method for modeling core-level photoelectron spectra in aqueous environments.This work poses a broader question: To what extent can LJ-PES complement established structuraltechniques such as nuclear magnetic resonance? Answering this question is highly relevant in viewof the large number of incorrect molecular structures published.